Drafting machine



Dec. 8, 1964 D. R. BRUNELL DRAFTING MACHINE Filed 001;- l'T, 1963 INVENTOR DAVID R- BRUNELL ATTORNEY United States Patent 3,159,919 DRAFTENG MACHINE David R. Brunell, 483 Pleasant St, Worcester, Mass. Filed Oct. 17, 1963, Ser. No. 317,001 2 Claims. (Cl. 33-79) This invention relates to drafting machines or instruments of the type including a protracto'r head which mounts two mutually perpendicular rules and being supported in turn by a system of interconnected and pivoted parallelogram link devices which permit the pair of rules to be displaced in parallelism to themselves throughout the extent of the drawing area.

The principal object of the invention resides in the provision of a machine or instrument of the above described type in which the two rules may be set at various.

intermediate angles and including mechanism for automatically locking the same at any selected angle at intervals with respect to the support therefor; in combination with means for interdicting the effect of the automatic locking mechanism so as to allow free manual rotation of the rules relative to the base upon which they are mounted, to any desired intermediate point.

The invention further relates to arrangements and combinations of parts which will be hereinafter described and more particularly set forth in the appended claims.

Reference is to be had to the accompanying drawings, in which:

FIG. 1 is a plan View illustrating the invention as applied to a conventional drawing board;

FIG. 2 is a plan view of the protractor and indexing mechanism on an enlarged scale, with parts in section and parts broken away;

FIG. 3 is a central vertical section on line 3-5 of FIG. 1 illustrating the releasing and locking mechanism;

FIG. 4 is a diagrammatic view illustrating one of the locking notches on an enlarged scale;

FIG. 5 is a bottom plan view of the finger-button which controls the locking, and

FIG. 6 is a side elevational veiw, partly in section, illustrating the button of FIG. 5.

Referring now to FIG. 1, there is shown a drawing board 10 upon which the drafting machine of the present invention is mounted. The reference numeral 12 indicates a clamp which can be applied in fixed condition anywhere along any edge of the drawing board and on this clamping member there is mounted a pair of pivoted links 14, 14 forming a parallelogram; The opposite ends of these links are pivotally secured with respect to a 'disc 16 and to the disc 16 there is pivotally mounted another pair of links 18, 18 forming another parallelogram. These links are pivotally secured with respect to a circular protractor element generally indicated by the reference numeral 29 as shown in scale at 22, 22 in FIG. 2. e

As shown in FIG. 3, the protractor 20 has a type of conical portion at the edge thereof which is properly embossed at the upper surface in degrees (FIG. 2), and at the under side of the periphery thereof there is provided a series of notches which are indicated at 24. As a practical embodiment, these notches occur at each fifteen degrees but this is a matter of convenience. Each notch 24 is provided with converging side walls (see FIG. 4).

The protractor element 26 is appropriately mounted for rotation on a stem 26 on a base member indicated generally at 28. This base member has secured thereto a pair of rigid arms 39, 32 upon which rules 34, 36 are conveniently mounted, the arms 3t), 32 being at right angles with respectto each other. A manipulating meniber or knob 38 may be provided secured to the stem 26- by means such as setscrew. 4!), whereby "the base 2.8 to- 3,159,919 Patented Dec. 8, 1964 gether with its arms 39 and 32 is rotatable under influence of the knob 33, the protractor 2% remaining in position as respects the two pivots 2.2. At the same time of course the entire base, protractor, etc. can be moved substantially anywhere about the surface of the drawing board id as is well known in the art.

Mounted by any desired means such as for instance rivets 42 there is a leaf spring 44 which is radially mounted on the base 28 and extends outwardly past the periphcry of protractor 29. This leaf spring has a width substantially the same as the bottoms of the notches 24 and it will be seen that as the spring is depressed from its normal position in a notch, the knob 38 and base 28 can be rotated. The spring will when released spring into the next notch 24 about the periphery of the protractor and is accurately seated so that the device is'accurately adjusted by reason of the converging edges of the slots 24.

Mounted on the base 28 adjacent the junction of the arms 30 and 32, there is a thumbpiece or button 46 which has a shank 48 and on the free end of the shank there is a cap 54), this cap being slightly larger in diameter than theshank 48 so that when assembled with a bushing generally indicated at 52, the button will not become disassembled.

The shank 48 is cylindrical but at its lower portion it has a square area portion 54. The bushing 52 has a hole in it through which the stem projects, this hole having a semicylindrical portion 56 and a square portion 58. Thus when a square portion 54 of the shank 48 is aligned with a square portion 58 of the hole in the bushing 52, the button 46 can be raised and lowered throughout its entire extent as indicated by the dotted line in FIG. 6. However, when a square portion 54 oi the shank 48 is aligned with the cylindrical portion of the hole in the bushing, then the corners of the square portion of the shank act as a stop and prevent any motion between the button and the bushing so that the parts are necessarily therefore in the solid line position shown in FIG. 6.

In the showing in FIGS. 2 and 3, the square portion 54- of shank 48 is aligned with the square portion of the hole in the bushing, and the button can be pushed down against the action of the spring 44, pushing the latter out of engagement with its notch, whereupon the knob 38 can be turned to any degree desired. When the button is released, the spring 44 will cause return to the solid line positions (see FIG. 3) and the spring 44 snaps into the next notch 24 as the base is continued to be rotated relative to the protractor, thus automatically latching the base with respect to the protractor in the desired location.

On the other hand, if it is desired to completely free the base from the protractor, all that is necessary to do is to depress the button 46 and then turn it with respect to the position shown in FIGS. 2 and 3. The thumb-button 46 will then be locked in its downwardmost position interdicting the action of spring 44 so that. it is out of the way and will not interfere with rotative motion of the base 28. c

Having thus described my invention and the advantages thereof, I do not wish to be limited to the details herein disclosed, otherwise than as set forth in the claims, but

a protractorpivotally connected to the freeends of the other pair of links, a base plate under the pr'otractor and. pivotally arranged with respect thereto, a pair of rules.

fixed to said base plate, saidprotractor being provided with a series of peripheral notches, said notches opening w 3 in a downward direction and facing the baseplate, a leaf spring fixedly mounted at one end thereof on said base plate and extending under the protractor in a radial direction with respect thereto and past the peripheral edge thereof, said leafspring having a width substantially equal to the width of each or said notches, said leaf spring normally being held by its inherent resilience in a notch, locking the base member relative to the protractor, a manually operable axially movable button mounted on said base plate, adjacent the periphery of the protractor, said button including an end in position to rest on the extending end of said leaf spring and being adapted to move the same out of its notch upon depression of the button, whereby the base plate may be rotated to a desired degree with respect to said protractor, and upon release of the button the spring is free to enter a selected notch, returning the manually operated button, each notch being provided with converging side walls which act to center the spring with reference to the notch, the Width of the spring being substantially equal to the narrowest portion of each notch.

4, 7 so that the button may be latched by said mounting means in a depressed position interdicting the action of the spring with respect to said notches, said button mounting means comprising a bushing having an aperture, said aperture having a semicylindn'cal portion and a rectangular portion, said shank having a corresponding semicylindrical portion, the projection on the shank including a rectangular portion thereon, whereby when the portions of the shank are aligned With respect to the corresponding portions of the aperture in the bushing, the shank is freely slidable therein, but when the shank is turned 180 so that the rectangular portion thereof corresponds with the cylindrical portion of the aperture in the bushing the button is maintained in its depressed position interdicting the spring.

' References Cited by the Examiner UNITED STATES PATENTS 1,408,252 2/22 Bieuville 33 79.3 1,797,213 3/31 Marcum 33 117 FOREIGN PATENTS 970,229 6/50 France.

ISAAC LISANN, Primary Examiner. 

1. A DRAFTING MACHINE COMPRISING IN COMBINATION A PAIR OF PIVOTALLY INTERCONNECTED PARALLELOGRAM STRUCTURES EACH COMPRISING A PAIR OF PARALLEL LINKS, MEANS PIVOTALLY CONNECTING THE LINKS IN PAIRS, AN ANCHORING DEVICE PIVOTALLY CONNECTED TO THE FREE END OF ONE OF SAID PAIRS OF LINKS, A PROTRACTOR PIVOTALLY CONNECTED TO THE FREE ENDS OF THE OTHER PAIR OF LINKS, A BASE PLATE UNDER THE PROTRACTOR AND PIVOTALLY ARRANGED WITH RESPECT THERETO, A PAIR OF RULES FIXED TO SAID BASE PLATE, SAID PROTRACTOR BEING PROVIDED WITH A SERIES OF PERIPHERAL NOTCHES, SAID NOTCHES OPENING IN A DOWNWARD DIRECTION AND FACING THE BASEPLATE, A LEAF SPRING FIXEDLY MOUNTED AT ONE END THEREOF ON SAID BASE PLATE AND EXTENDING UNDER THE PROTRACTOR IN A RADIAL DIRECTION WITH RESPECT THERETO AND PAST THE PERIPHERAL EDGE THEREOF, SAID LEAF SPRING HAVING A WIDTH SUBSTANTIALLY EQUAL TO THE WIDTH OF EACH OF SAID NOTCHES, SAID LEAF SPRING NORMALLY BEING HELD BY ITS INHERENT RESILIENCE IN A NOTCH, LOCKING THE BASE MEMBER RELATIVE TO THE PROTRACTOR, A MANUALLY OPERABLE AXIALLY MOVABLE BUTTON MOUNTED ON SAID BASE PLATE, ADJACENT THE PERIPHERY OF THE PROTRACTOR, SAID BUTTON INCLUDING AN END IN POSITION TO REST ON THE EXTENDING END OF SAID LEAF SPRING AND BEING ADAPTED TO MOVE THE SAME OUT OF ITS NOTCH UPON DEPRESSION OF THE BUTTON WHEREBY THE BASE PLATE MAY BE ROTATED TO A DESIRED DEGREE WITH RESPECT TO SAID PROTRACTOR, AND UPON RELEASE OF THE BUTTON THE SPRING IS FREE TO ENTER A SELECTED NOTCH, RETURNING THE MANUALLY OPERATED BUTTON, EACH NOTCH BEING PROVIDED WITH CONVERGING SIDE WALLS WHICH ACT TO CENTER THE SPRING WITH REFERENCE TO THE NOTCH, THE WIDTH OF THE SPRING BEING SUBSTANTIALLY EQUAL TO THE NARROWEST PORTION OF EACH NOTCH. 